1. Field of the Invention
The invention relates to a chopper circuit for driving of electromagnet and/or step motor coils, in particular as employed in a matrix printer, where the inductivity of the coils in connection with the applied voltage generates a maximum current, which maximum current, however, is set lower by a desired factor, where the current ripples can be generated by chopping.
2. Brief Description of the Background of the Invention Including Prior Art
The control and driving of electromagnetic coils in matrix print heads is performed with driver circuits, the purpose of which is to build up the magnetic field as quickly as possible and to let decay unavoidable counter inductions physically as quickly as possible during decline (German Patent DE-PS 31 39 502). In this context the object is desired to be able to pass renewed current through the electromagnetic coil in order to effect the renewed shooting of one and the same print needle in shorter time intervals, that is to achieve a quicker printing process.
Other solutions for the driving of electromagnetic coils in printers attempt to avoid an overcurrent passage (German Patent Application Laid Open DE-OS 31 51 242), in order to avoid the damaging lost heat in the coil. This lowering of the lost heat increases the lifetime of such matrix print heads.
It is a joint feature of the conventional solutions to keep the current flowing times as short as possible for reducing the lost heat and to allow a quick reinitiation of the current for a quick shooting of a printer needle.
Now, additional points of consideration have been found with regard to the requirement that different inductivities of electromagnetic coils and magnet coil windings in step motors require on the one hand an adaptation of the frequency and on the other hand the two types of coils can be driven in a system based on the same principals by one chopper circuit.